The present invention concerns the manufacturing of molds, generally metallic, for curing and molding tire raw carcasses. A mold for tire molding includes different types of protrusions on its surface, so that pressing a raw tire against the surface of the mold in the tread band of the tire a protruding design is obtained. However when a raw tire is pressed against the surface of the mold, there is air between the surface of the mold and the tire and thus, since the design is formed with protrusions from the surface of the mold, the air contained between mold and tire has no way to escape and remains thus trapped. Consequently on the surface of the cured tire depressions appear as small hollows, technically known as a "shortage" but hereinafter simply called "bubbles" that reduce the commercial value of the tire.
To eliminate such air hollows (bubbles) the thoroughgoing holing or microfissures methods are usually used or a combination between them, according to which the metallic mold is provided with very small holes or thin fissures, piercing radially the body of the mold or the transverse holes or slots method according to which in the protrusion bodies holes or thin slots are made that cross right through the protrusion body. However, when using thoroughgoing holes or similar contrivances, a finishing operation is necessary because also the rubber enters these openings producing rubber protrusions (burrs) on the surface of the tire and so it is also necessary to use a further separate device to eliminate the said burrs. However, even after the burrs have been removed, their trail remains and the product is still adversely affected. In the case of the holes or of transverse slots in the protrusions or similar contrivances, there is the disadvantage that it is difficult to remove completely the air hollows between the protrusions. Also in the grooves of the tread, rubber protrusions are formed constituted by the burrs, that compromise the desirability of the tire.